This invention relates generally to turbomachines and in particular to an actuator for the adjustable vanes of a turbomachine.
Turbomachines, such as compressors, turbines, and expanders, utilize adjustable vanes or blades of many types. For example, adjustable vanes are employed as prewhirl devices and as antiwhirl devices. In addition, stator vanes of an axial compressor are very often adjustable as are inlet nozzle vanes.
Generally, adjustable vanes are moved in unison by actuators such as linkage arrangements connected to a movable ring which, when rotated, moves the adjustable vanes in the desired manner through the associated linkage arrangement. Actuators of the foregoing type are relatively expensive to manufacture and are subject to frictional and backlash problems. In addition, the aforedescribed actuators generally require a significant amount of maintenance to maintain such actuators trouble-free.
In the 1960's, as a result of work performed through NASA, a new relatively friction-free bearing was developed. This device is known as a "Rolamite". A Rolamite bearing is relatively frictionless, and has zero backlash. In effect, a Rolamite eliminates almost all sliding friction and generates only rolling friction. Further, the Rolamite is a relatively inexpensive and maintenance free device. Surprisingly, the Rolamite has not achieved the wide-spread and diverse use originally forecast and as would be expected, perhaps due to a general inability on the part of design engineers to comprehend the applicability of the device for diverse applications.